Nitrogen control method for smelting sulfur-containing gear steel by ecological electric furnace

Abstract

The invention discloses a nitrogen control method for smelting sulfur-containing gear steel by an ecological electric furnace, which specifically comprises the following steps: adding a nitrogen-containing alloy during alloying according to one-time total analysis of components in an LF (ladle furnace) refining process, and obviously facilitating the reduction of the production cost because the nitrogen-containing alloy is alloyed together with other alloys, so that the production cost is reduced. In the process, even if the molten steel temperature drop problem occurs, the subsequent RH vacuum degassing process is not influenced, so that compared with a traditional nitrogen control process, the nitrogen-containing alloy is added in the LF refining process, the burning loss can be reduced, the yield can be increased, and the smelting time can be saved; furthermore, in the RH vacuum cycle degassing step, nitrogen is used as lifting gas and is softly blown to increase nitrogen, so that the loss of the nitrogen element is reduced; therefore, according to the nitrogen control method, the purpose of accurately controlling the nitrogen content in the gear steel is achieved on the premise that the treatment time is not increased and the smelting cost is reduced, and a certain application value is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a nitrogen-controlled process for smelting sulfur-containing gear steel in an ecological electric furnace. Background Art

[0002] Mn-Cr gear steel is a gear steel grade introduced from Germany. It is widely used in domestic Audi, Jetta and other cars. It is a high-standard car gear steel. 20MnCrS5-2 steel is one of them. It belongs to carburizing steel and can be used after quenching and tempering. This steel has good terminal hardenability, small deformation during heat treatment, excellent low-temperature toughness and cutting performance, etc. It can be used as carburized parts and quenched and tempered parts with large cross-sections. Due to its high requirements on the purity of molten steel, and this series of steel grades are nitrogen-containing steel grades, requiring a nitrogen content of 80-140ppm, it is a difficult problem to accurately control the nitrogen content during the smelting process. Usually, manganese nitride and chromium nitride alloys are added after vacuum to adjust the nitrogen content in the steel. However, adding alloys after vacuum will prolong the smelting time, and the impurity elements in the alloy may have the risk of contaminating the molten steel. In addition, nitrogen addition through alloy alone will also increase production costs; if only bottom blowing nitrogen is used to increase nitrogen, the smelting soft blowing time will be increased, the molten steel temperature and production rhythm will be difficult to control, and the nitrogen addition effect will not be obvious. Therefore, it is necessary to develop a low-cost nitrogen control process to reduce production costs and achieve the purpose of precise nitrogen control. Summary of the invention

[0003] In view of this, the present disclosure provides a nitrogen control method for smelting sulfur-containing gear steel in an ecological electric furnace to solve the problems of production cost and inability to accurately control the current nitrogen control process.

[0004] To achieve the above-mentioned invention object, the method for controlling nitrogen in smelting sulfur-containing gear steel in an ecological electric furnace comprises:

[0005] In the LF refining process, when alloying is performed according to the first full analysis composition, a nitrogen-containing alloy is added to increase nitrogen, and the amount of the nitrogen-containing alloy added is determined according to the first full analysis composition.

[0006] In the present disclosure and possible embodiments, the nitrogen-containing alloy is manganese nitride.

[0007] In the present disclosure and possible embodiments, the method for controlling nitrogen in smelting sulfur-containing gear steel in an ecological electric furnace further includes:

[0008] In the RH vacuum degassing process, nitrogen is used as the lifting gas and the static blowing gas.

[0009] In the present disclosure and possible embodiments, when alloying is performed according to a full analysis composition, 0.6-1.0 kg / t of ferrosilicon, 2-3 kg / t of medium carbon ferromanganese, 3-4 kg / t of low carbon ferrochrome, 1-3 kg / t of alumina balls, 1-2 kg / t of electrolytic nickel and the nitrogen-containing alloy are added, and argon is blown into the bottom of the process ladle for stirring.

[0010] In the present disclosure and possible embodiments, in the LF refining process, after the ladle for smelting in the ecological electric furnace is in place, the argon gas is turned on with a flow rate of 300 to 500 NL / min. The ladle is opened to the smelting station to add lime, and power is started for 3 to 5 minutes. After the thin slag is formed, the argon gas flow rate is adjusted to 150 to 250 NL / min, and 1.4 to 1.6 kg / t of aluminum wire segments are added for diffusion deoxidation, and silicon carbide is added in batches.

[0011] In the present disclosure and possible embodiments, after alloying is completed according to the primary full analysis composition, the argon flow rate is adjusted to 100-200NL / min after the secondary full analysis composition is adjusted, and the argon flow rate is adjusted to 30-60NL / min during the static blowing waiting period.

[0012] In the present disclosure and possible embodiments, in the RH vacuum degassing process, after the ladle is placed on the ladle car, the argon gas is opened and blown, with a flow rate of 300-450NL / min. After entering the working position, the jacking operation is started, the insertion depth of the immersion tube is greater than 400mm, the argon gas is turned off, the vacuum degree is <100Pa, and the duration is ≥15min. The lifting gas is switched to nitrogen, and calcium treatment is carried out after breaking the air. Nitrogen is blown quietly at 10-60NL / min, the stirring time is 15-20min, not more than 30min, and the covering agent is added to complete the RH vacuum degassing.

[0013] In the present disclosure and possible embodiments, the ecological electric furnace smelting adopts scrap steel and molten iron for smelting, with the proportion of molten iron added being about 55%, and the molten iron temperature being required to be ≥1250°C;

[0014] The scrap steel is added into the vertical furnace once every 3 to 5 minutes by the secondary system of the ecological electric furnace, and the scrap steel is pushed into the molten pool after being preheated in the vertical furnace; after the scrap steel is preheated to 600 to 800° C. by the flue gas in the furnace, it is pushed into the smelting area in the furnace by the steel pusher, oxygen is blown to assist melting, and lime and magnesite are added for slag making operation;

[0015] When the final carbon content is 0.05-0.10%, the final P≤0.018%, the residual elements satisfy Cu≤0.09%, Mo≤0.02%, and the temperature is 1600-1630°C, steel tapping begins; the argon flow rate is adjusted to 500-750L / min during steel tapping, and the argon flow rate is adjusted to ≤150L / min after steel tapping.

[0016] In the present disclosure and possible embodiments, the steel tapping time is controlled at 5 to 6 minutes. When 15 to 20 tons of steel are tapped, the baked alloys are added in sequence at a baking temperature of 600 to 800°C. The alloys are 1.0 to 1.5 kg / t of aluminum segments, 11.0 to 13.0 kg / t of medium carbon ferromanganese, 2.0 to 3.0 kg / t of high carbon ferrochrome and 13.0 to 15 kg / t of low carbon ferrochrome. 6.0 kg / t of ladle lime and 4.6 kg / t of synthetic slag are added.

[0017] In the present disclosure and possible embodiments, the molten steel after RH vacuum degassing is subjected to continuous casting and hot rolling to obtain the sulfur-containing gear steel.

[0018] The present invention has the following beneficial effects:

[0019] The method for controlling nitrogen in smelting sulfur-containing gear steel in an ecological electric furnace of the present invention changes the traditional method of feeding manganese nitride cored wire for nitrogen addition after RH is completed, and instead adds nitrogen-containing alloy during alloying according to a full analysis composition in the LF refining process. The price of nitrogen-containing alloy is lower than that of manganese nitride cored wire, which is obviously beneficial to reducing production costs. At the same time, because the nitrogen-containing alloy is alloyed together with other alloys, even if the temperature drop of molten steel occurs in this process, it has no effect on the subsequent RH vacuum degassing process. Therefore, compared with the traditional nitrogen control process, adding nitrogen-containing alloy in the LF refining process can reduce burning loss, increase yield and save smelting time; further, nitrogen is used as a lifting gas and soft nitrogen blowing is used to increase nitrogen in the RH vacuum cycle degassing step, which reduces the loss of nitrogen element; in summary, the nitrogen control method of the present invention achieves the purpose of accurately controlling the nitrogen content in gear steel without increasing the processing time and reducing the smelting cost, and has application value. DETAILED DESCRIPTION

[0020] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure. At the same time, unless the context clearly requires, the words "including", "comprising" and the like in the entire specification and claims should be interpreted as including rather than exclusive or exhaustive meanings; that is, the meaning of "including but not limited to".

[0021] The prior art adopts a nitrogen-increasing method of feeding nitrogen-containing cored wire or bottom blowing nitrogen into the molten steel after vacuum. First, feeding manganese nitride cored wire to increase nitrogen after RH is finished can prevent alloy oxidation and stabilize the nitrogen content of molten steel, but the price of nitrogen manganese wire is relatively expensive, resulting in increased production costs. Secondly, the inventor observed that the temperature of the molten steel dropped during the wire feeding process, and the temperature of the molten steel entering the RH station needs to be increased, which is not conducive to the maintenance of the ladle refractory, and also increases the LF power-on time, resulting in an increase in smelting power. In addition, if nitrogen is increased simply by bottom blowing nitrogen, the nitrogen content in the molten steel increases slowly, and after RH vacuum cycle degassing (using argon as a lifting gas), the inventor also found that the nitrogen content in the molten steel will have a certain loss, and the yield cannot be guaranteed. To solve the above problems, the present invention adopts a nitrogen-increasing method of adding nitrogen-containing alloys in the LF refining process to reduce the nitrogen-increasing cost and process time. In addition, RH vacuum cycle degassing uses nitrogen as a lifting gas and soft blowing gas, the purpose of which is to reduce the loss of nitrogen elements.

[0022] This disclosure takes the production of 20MnCrS5-2 gear steel as an example to specifically illustrate the nitrogen control method for smelting sulfur-containing gear steel in an ecological electric furnace according to the present invention. The method steps are as follows:

[0023] 1. The chemical composition of molten steel for producing 20MnCrS5-2 gear steel is as follows:

[0024] C: 0.17%~0.20%, Si≤0.25%, Mn: 1.10%~1.30%, P≤0.025%, S: 0.020~0.035%, Alt: 0. 020~0.040%, Ti: ≤0.010%, Cr: 1.00~1.20%, Mo≤0.08%, Ni: 0.10~0.25%, Cu≤0.25%.

[0025] 2. The production process of ecological electric furnace smelting → LF → RH → continuous casting → heating → rolling is adopted, among which:

[0026] (1) Ecological electric furnace smelting:

[0027] The ecological electric furnace uses scrap steel and molten iron for smelting, with the molten iron ratio being about 55% and the molten iron temperature required to be ≥1250℃.

[0028] The secondary system of the ecological electric furnace adds scrap steel into the vertical furnace every 3 to 5 minutes, and the scrap steel is preheated in the vertical furnace and pushed into the molten pool. The entire smelting process is added 3 to 4 times, with a total scrap steel amount of 35 to 45 tons.

[0029] After the scrap steel is preheated to 600-800℃ by the flue gas in the furnace, it is pushed into the smelting area of ​​the furnace by the steel pusher. According to the situation in the furnace, the furnace door oxygen gun is opened and the flow rate is adjusted to 2500Nm 3 / h, blow oxygen to assist melting, add 44-46kg / t of lime and 10-13kg / t of magnesite to carry out slag making operation.

[0030] When the final carbon is 0.05-0.10%, the final P≤0.018%, the residual elements satisfy Cu≤0.09%, Mo≤0.02%, and the temperature is 1600-1630℃, steel tapping begins.

[0031] When tapping steel, the argon flow rate is adjusted to 500-750L / min. After tapping steel, the argon flow rate is adjusted to ≤150L / min. The argon gas is turned off before the ladle is hung. The purpose is to strictly prohibit excessive bottom blowing that will cause the steel liquid surface to be exposed.

[0032] The tapping time is controlled at 5-6 minutes. When 15-20 tons of steel are tapped, the baked alloys are added in sequence at a baking temperature of 600-800°C to reduce the entry of foreign gas into the molten steel. Among them, 1.0-1.5 kg / t of aluminum wire segments, 11.0-13.0 kg / t of medium carbon ferromanganese, 2.0-3.0 kg / t of high carbon ferrochrome, 13.0-15 kg / t of low carbon ferrochrome, 6.0 kg / t of ladle lime and 4.6 kg / t of synthetic slag are added.

[0033] (2) LF refining:

[0034] After the ladle is in place, turn on the argon gas with a flow rate of 300-500NL / min. The ladle is opened to the smelting station to add 350-500kg of lime, and power is supplied for 3-5 minutes. After the thin slag is formed, the argon gas flow rate is adjusted to 150-250NL / min. The purpose is to prevent large flow of argon gas from stirring and heating. According to the slag condition, 1.4-1.6kg / t of aluminum wire segments can be added for diffusion and deoxidation. At the same time, 50-80kg of silicon carbide is added in the first batch, and power is supplied for 5-8 minutes. 20-50kg of silicon carbide is added in the second batch. The total amount of silicon carbide added is 150-210kg / furnace.

[0035] After the furnace door is closed and the power is supplied for ≥20min, dip the slag to confirm that the slag is white, measure the temperature and take a sample. According to the first full analysis composition, alloying is carried out, adding 0.6-1.0kg / t of ferrosilicon, 2-3kg / t of medium carbon ferromanganese, 3-4kg / t of low carbon ferrochrome, 1-3kg / t of alumina balls, 1-2kg / t of electrolytic nickel, and adding manganese nitride to increase nitrogen. During the process, argon is blown at the bottom of the ladle for stirring. After the adjustment of the second full analysis composition is completed, the argon gas is adjusted to 100-200NL / min; the argon gas flow rate is adjusted to 30-60NL / min during the static blowing waiting period.

[0036] (3) RH vacuum degassing:

[0037] After the ladle is placed on the ladle car, turn on the argon gas to blow it open, with a flow rate of 300-450NL / min. After entering the working position, start the jacking operation, the immersion tube insertion depth is greater than 400mm, turn off the argon gas, the vacuum degree is <100Pa, the duration is ≥15min, the lifting gas is switched to nitrogen, and calcium treatment is carried out after breaking the air. The static argon gas is switched to nitrogen, the stirring time is 15-20min, not more than 30min, and 6-8 bags of covering agent are added; static nitrogen blowing is 10-60NL / min, and the static blowing should be done with slight movement of the slag surface and no exposure of the molten steel.

[0038] (4) Continuous casting:

[0039] The vacuum degassed molten steel is hoisted to the casting position, and the molten steel pulling speed is controlled according to Table 1. The continuous casting ladle adopts a continuous slag detection device to prevent slag from falling. The electromagnetic stirring parameters are shown in Table 2, and the protective slag adopts low-carbon titanium steel protective slag.

[0040] Table 1 Superheat control range

[0041]

[0042] Table 2 Electromagnetic stirring parameters

[0043]

[0044] Example 1

[0045] According to the nitrogen control method of the present invention, 20MnCrS5-2 is prepared, and the specific process is as follows:

[0046] 1. Chemical composition of 20MnCrS5-2 gear steel by weight percentage:

[0047] C: 0.17%~0.20%, Si≤0.25%, Mn: 1.10%~1.30%, P≤0.025%, S: 0.020~0.035%, Alt: 0. 020~0.040%, Ti: ≤0.010%, Cr: 1.00~1.20%, Mo≤0.08%, Ni: 0.10~0.25%, Cu≤0.25%.

[0048] 2. The production process of ecological electric furnace smelting → LF → RH → continuous casting → heating → rolling is adopted, as follows:

[0049] (1) Ecological electric furnace smelting:

[0050] The ecological electric furnace uses scrap steel and molten iron for smelting, with 50.5t of molten iron at a temperature of 1310℃ and 40.2t of scrap steel.

[0051] After the scrap steel is preheated in the vertical furnace, the secondary system of the ecological electric furnace adds one car of scrap steel into the vertical furnace every 3 to 5 minutes. A total of 4 cars are added during the entire smelting process, and each car has 10 tons of scrap steel.

[0052] After the scrap steel is preheated to 600-800℃ by the flue gas in the furnace, it is pushed into the smelting area of ​​the furnace by the steel pusher. According to the situation in the furnace, the furnace door oxygen gun is opened and the flow rate is adjusted to 2500Nm 3 / h, blow oxygen to assist melting, add 4500kg of lime and 1300kg of magnesite to carry out slag making operation.

[0053] When the end point C: 0.058%, the end point P: 0.005%, the residual element Cu: 0.04%, Mo≤0.01%, and the temperature 1622℃, steel tapping begins.

[0054] When tapping steel, the argon flow rate is adjusted to 500-750L / min. After tapping steel, the argon flow rate is adjusted to ≤150L / min. The argon gas is turned off before the ladle is hung. It is strictly forbidden to blow too much bottom gas to expose the molten steel surface.

[0055] The steel tapping time is controlled at 6 minutes. When 20 tons of steel is tapped, the baked alloys are added in sequence. The baking temperature is 600-800℃ to reduce the entry of foreign gas into the molten steel. Among them, 1.4 kg / t of aluminum wire segments, 12.3 kg / t of medium carbon ferromanganese, 2.1 kg / t of high carbon ferrochrome, 14.2 kg / t of low carbon ferrochrome, 6.0 kg / t of ladle lime and 4.6 kg / t of synthetic slag are added.

[0056] (2) LF refining:

[0057] After the ladle is in place, turn on the argon gas with a flow rate of 300-500NL / min. The ladle is opened to the smelting station to add 500kg of lime, and power is supplied for 4 minutes. After the thin slag is formed, the argon gas flow rate is adjusted to 150-250NL / min. The purpose is to prevent large argon gas stirring and heating. According to the slag condition, 150kg of aluminum wire segments are added for diffusion and deoxidation. At the same time, 60kg of silicon carbide is added in the first batch, and power is supplied for 7 minutes; 40kg of silicon carbide is added in the second batch. The total amount of silicon carbide added during the refining process is 180kg.

[0058] After the furnace door is closed and the power is supplied for ≥20min, dip the slag to confirm that the slag is white, measure the temperature and take a sample. According to the first full analysis composition, alloying is carried out, adding 0.7kg / t of ferrosilicon, 2.2kg / t of medium carbon ferromanganese, 3.8kg / t of low carbon ferrochrome, 1.5kg / t of alumina balls, 1.2kg / t of electrolytic nickel, and 163kg of manganese nitride to increase nitrogen. During the process, argon is blown at the bottom of the ladle for stirring. After the adjustment of the second full analysis composition is completed, the argon gas is adjusted to 100-200NL / min; the argon gas flow rate is adjusted to 30-60NL / min during the static blowing waiting period.

[0059] (3) RH vacuum degassing:

[0060] After the ladle is placed on the ladle car, turn on the argon gas to blow it open, with a flow rate of 300-450NL / min. After entering the working position, start the jacking operation, the immersion tube insertion depth is greater than 400mm, turn off the argon gas, the vacuum degree is <100Pa, the duration is ≥15min, the lifting gas is switched to nitrogen, and calcium treatment is carried out for 84m after breaking the air. The static blowing of argon gas is switched to nitrogen, the stirring time is 16min, and 6 bags of covering agent are added; static blowing of nitrogen is 10-60NL / min, and static blowing is carried out so that the slag surface moves slightly and the molten steel is not exposed.

[0061] (4) Continuous casting:

[0062] The vacuum degassed molten steel is hoisted to the casting position, and the molten steel pulling speed is controlled according to Table 1. The continuous casting ladle adopts a continuous slag detection device to prevent slag from falling. The electromagnetic stirring parameters are shown in Table 2, and the protective slag adopts low-carbon titanium steel protective slag.

[0063] After the process is completed, the chemical composition of the 20MnCrS5-2 gear steel prepared in this Example 1 is shown in Table 3:

[0064] Table 3 Chemical composition of Example 1 of the present invention %

[0065] Example C Si Mn P S Cr Mo Ni Cu Alt N 1 0.186 0.22 1.27 0.016 0.025 1.15 0.01 0.13 0.04 0.029 0.0101

[0066] It can be seen from the data in Table 3 that after the implementation of the present invention, the nitrogen content is controlled at 101 ppm, meeting the requirement of 80 to 140 ppm.

[0067] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A nitrogen control method for smelting sulfur-containing gear steel in an ecological electric furnace, characterized in that: include: In the LF refining process, when alloying is performed according to the first full analysis composition, a nitrogen-containing alloy is added to increase nitrogen, and the amount of the nitrogen-containing alloy added is determined according to the first full analysis composition.

2. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 1, characterized in that: The nitrogen-containing alloy is manganese nitride.

3. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 1 or 2, characterized in that: Also includes: In the RH vacuum degassing process, nitrogen is used as the lifting gas and the static blowing gas.

4. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 3, characterized in that: When alloying according to the first full analysis composition, add 0.6-1.0kg / t of ferrosilicon, 2-3kg / t of medium carbon ferromanganese, 3-4kg / t of low carbon ferrochrome, 1-3kg / t of alumina balls, 1-2kg / t of electrolytic nickel and the nitrogen-containing alloy, add argon gas to the bottom of the process ladle for stirring.

5. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 4, characterized in that: In the LF refining process, after the ladle for smelting in the ecological electric furnace is in place, the argon gas is turned on with a flow rate of 300-500NL / min. The ladle is opened to the smelting station to add lime, and power is supplied for 3-5 minutes. After the thin slag is formed, the argon gas flow rate is adjusted to 150-250NL / min, and 1.4-1.6kg / t of aluminum wire segments are added for diffusion deoxidation, and silicon carbide is added in batches.

6. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 4 or 5, characterized in that: After alloying is completed according to the first full analysis composition, the argon flow rate is adjusted to 100-200NL / min after the second full analysis composition is adjusted, and the argon flow rate is adjusted to 30-60NL / min during the static blowing waiting period.

7. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 6, characterized in that: In the RH vacuum degassing process, after the ladle is placed on the ladle car, the argon gas is turned on and blown open with a flow rate of 300-450NL / min. After entering the working position, the jacking operation is turned on, the insertion depth of the immersion tube is greater than 400mm, the argon gas is turned off, the vacuum degree is <100Pa, and the duration is ≥15min. The lifting gas is switched to nitrogen, and calcium treatment is carried out after breaking the air. Nitrogen is blown quietly at 10-60NL / min, the stirring time is 15-20min, not more than 30min, and the covering agent is added to complete the RH vacuum degassing.

8. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 5, characterized in that: The ecological electric furnace smelting adopts scrap steel and molten iron, with the proportion of molten iron added being about 55%, and the molten iron temperature being required to be ≥1250°C; The scrap steel is added into the vertical furnace once every 3 to 5 minutes by the secondary system of the ecological electric furnace, and the scrap steel is pushed into the molten pool after being preheated in the vertical furnace; after the scrap steel is preheated to 600 to 800° C. by the flue gas in the furnace, it is pushed into the smelting area in the furnace by the steel pusher, oxygen is blown to assist melting, and lime and magnesite are added for slag making operation; When the final carbon content is 0.05-0.10%, the final P≤0.018%, the residual elements satisfy Cu≤0.09%, Mo≤0.02%, and the temperature is 1600-1630°C, steel tapping begins; the argon flow rate is adjusted to 500-750L / min during steel tapping, and the argon flow rate is adjusted to ≤150L / min after steel tapping.

9. The method for controlling nitrogen in smelting sulfur-containing gear steel using an ecological electric furnace according to claim 8, characterized in that: The steel tapping time is controlled at 5 to 6 minutes. When 15 to 20 tons of steel are tapped, the baked alloys are added in sequence at a baking temperature of 600 to 800° C. The alloys are 1.0 to 1.5 kg / t of aluminum wire segments, 11.0 to 13.0 kg / t of medium carbon ferromanganese, 2.0 to 3.0 kg / t of high carbon ferrochrome and 13.0 to 15 kg / t of low carbon ferrochrome. 6.0 kg / t of ladle lime and 4.6 kg / t of synthetic slag are also added.

10. The method for controlling nitrogen in smelting sulfur-containing gear steel in an ecological electric furnace according to any one of claims 6 to 9, characterized in that: The molten steel after RH vacuum degassing is subjected to continuous casting and hot rolling to obtain the sulfur-containing gear steel.

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